Certain conditions may preclude specific procedures included in this protocol, but may still allow pertinent parts of the diagnostic evaluation. These conditions/procedures may include: pregnancy/chest radiograph. For reversible conditions, such as acute upper airway infection, significant epistaxis within the prior week (not related to number 2 below), or lower airway infection with uncontrollable coughing, the participant may need to be re-evaluated after resolution. For nasal NO or nasal mucosal scrapings, the following lists the absolute contraindications: